Running optional tasks

[Eric . Hardesty]

I downloaded Pvcs source compiled and put it into optional.jar, which is in
%ANT_HOME%\lib.
When I try to use <pvcs  /> I get
        Could not create task of type: pvcs. Common solutions are to use taskdef
        to declare your task, or, if this is an optional task , to put the
        optional.jar in the lib directory of your ant installation (ANT_HOME).

What am I doing wrong?

Eric